[Closed] Hydraulic disc brake noob questions 🙂

It's nigh on impossibleto shorten the hose without losing the fluid and you'll probably need to bleed them once you're done.So you'll need a bleed kit.

shimano use mineral oil IIRC.

You'll need at least new olives - you can sometimes get away with reusing old ones but for what they cost get new.

have a gander at this - [url= http://www.bikeradar.com/gear/article/workshop-how-to-fit-shimano-disc-brakes-18265/ ]SERVICE SHIMANO DISC BRAKES[/url] it might help

Thanks. I've got a bleed kit that came with the bike (at least I assume that's what it is - sort of funnel and tube). I'll get hold of some olives and fluid then before I do anything.

I'm pretty used to doing car brakes so I'm sure it'll be fine - I was just hoping it might be nice and quick and easy like the Maguras - not so it sounds :/

Not sure what model your brakes are, but you could try this method:

[url= http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50rparsys-0008-downloadFile.html/02%29%20Brake%20Hose%20Trimming.pdf ]http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/tech_tips.download.-Par50rparsys-0008-downloadFile.html/02%29%20Brake%20Hose%20Trimming.pdf[/url]

It's exactly the same fluid as Magura BTW - mineral oil.
I've given up on doing brakes, never happy with my own efforts, too fiddly, can't be arsed, only £15 to have it done properly, at my LBS.

Its easy enough to do. I've no idea how hard the Maguras are. Basically remove hose at the lever end, cut to correct length, fit new olive, reassemble, bleed. If you got the yellow funnel you probably also got a couple of spare olives?

The bleed instructions are in the manual (presume supplied with bike - but probably available on line). IIRC, Basically you will need a syringe, some flexible tubing and a small container (even a sandwhich bag).

You need to learn how to bleed and there is an art to it. Unless you are daft, you can learn this art. The art varies for all brakes. With Hayes it can get fun time nursery messy, but not without its virtues. Avid is very clean. Hope cleaner still. Shimano and Magura great if just for the fact they don't use DOT brake fluids.

You will need to bleed afterwards. You need to learn how to bleed. Watch a youtube video on it, read a forum post or 10 about it. Look at the Shimano manual. School thyself.

It's exactly the same fluid as Magura BTW - mineral oil.

Thanks for that - I thought the Magura fluid was some sort of silicone stuff, but it is indeed mineral oil as you say. I've got a bottle of Maggy blood somewhere, so that should do.

Not sure we got any spare olives and stuff in the bag with the funnel thing, but I'll have a better look before I buy some.

I've no idea how hard the Maguras are

The HS33/22/66 rim brakes, being a closed system with very thin capillary tubing, are possible to shorten the hose without bleeding being needed if you're careful. The fluid just sits there and doesn't come out unless you shake it, so you can just fit a new olive and reassemble without any air getting in. If you cock it up and some gets in then you have to bleed it, which is messy (but didn't take much "schooling of thyself"). I've shortened quite a few HS33 and 66 hoses and only ever had to bleed one once. Looks like bleeding will be pretty much inevitable with the Shimano stuff.

Best way to shorten hoses and avoiding bleeding is as follows.
1) Remove pads and carefully pull the brake lever so that the pistons come out of the caliper by about 2mm each side.
2) Unscrew the hose from the lever, wiggle it a little, then pull it out.
3) Cut the hose keeping it above the height of the caliper, fit the olive and barb, tighten the locking collar back up.
4) Remove fluid reservoir cover and then push both pistons back into the caliper (a plastic tyre lever is very good for this), bubbles should come out of the hose and hopefully some fluid (fluid level rises).
Check the action of the lever, it should be firm with no sponginess. If not a bleed it required.
Best way is to force fluid through the caliper up to the lever using a syringe connected to the bleed nipple with a length of clear hose.

It's nigh on impossibleto shorten the hose without losing the fluid

Really? maybe I've just been lucky the times I've done it then. 🙄

Shortened hoses twice without the need to bleed them afterwards.

OK, I'll give that method a go - nothing to lose really. Thanks for the hints.

I did some piccies on the other thread. Have a [url= http://www.singletrackworld.com/forum/topic/psa-xt-m785-brakes/page/6#post-2909210 ]gander[/url]

btw - [url= http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_204265_langId_-1_categoryId_165750 ]this[/url] save a lot of money. Hydraulic fluid, bottle lasts forever! Green instead of Shimano's pink.

I just think it's bad practice to shorten a hose and not rebleed at least the lever end afterwards.

An elastic band pulling the levers (doesn't have to be super tight) also hardens a brake between rides, especially overnight. Neat trick. Always feel just bled.

The "trick" to avoid needing to bleed after trimming is to squeeze the pistons forward a bit in their bores BEFORE cutting the hose, and then push them back afterwards.

Yep, done it 3 times with Shimano and never needed to bleed any of them.

That's subjective though surely? It's like not washing your hands after a poo and bum wipe. It will likely not hurt you, but it don't make it right.

You've exposed the system to air, therefore you should bleed. It might not make a huge amount of difference if you are lucky and/or skilfull, but it will unlikely leave the system at it's best. Maybe 90% of best if you are neat.

Don't forget Shimano brakes dont use dont fluid, so aren't going to be affected by air (and subsequent water absorbtion).
If the pistons are pushed out like I suggested, when fully retracted they should displace more than enough fluid to force any air back into the lever reservoir.

in which case it will need topping off, unless you are looking to see some weeping at the reservoir cap?

If by "topping off" you mean

4) Remove fluid reservoir cover and then push both pistons back into the caliper (a plastic tyre lever is very good for this), bubbles should come out of the hose and hopefully some fluid (fluid level rises).

Then its already been covered ^^^

OK, quick update. Did it last weekend - didn't get away with the "no bleeding" trick, but bleeding was easy (if a little bit more of a faff than with Maggy rim brakes, but only took a couple of minutes using a syringe and the "yellow funnel"). I couldn't find any official manual covering bleeding, but there's a tutorial video on Shimano's site that was quite useful.
(they're Deore M575 brakes BTW).

I didn't have the official Shimano "gripper" thing to hold the hose while inserting the barbed insert, but the Magura one happened to be the right size. I also chickened out of using Magura fluid even though it's supposedly almost the same stuff, as I found a few scare stories on the web about problems with mixing Shimano and Maggy oil - could be bollox but for the sake of £2 for a small bottle of proper Shimano oil off ebay it was never worth the risk in case of any warranty claims or whatever. On the subject of Shimano oil, why don't they sell it in sensible amounts? The bloke on ebay had obviously bought a big bottle and sold it off in small bottles at a profit, which suits me - I don't wan't a litre of it when there's only one disc braked bike in the family collection, and I don't want to pay nearly a tenner for 50ml either!

Bleeding brakes is so simple, I can't really see the point in trying to avoid doing it when shortening hoses
Air will have got in the system, whether it's enough to cause issues or not is often a bit random so a quick bleed is the best way to mitigate any possible problem